Electrochemical Properties of Assbs with High Energy Density Using Thin Solid Electrolyte Sheet

Abstract

Recently, the use of liquid electrolytes in lithium batteries is prone to cause safety problems such as leakage and gas explosions. The PEO-based solid composite electrolytes (CE) for all-solid state batteries (ASSBs) have been studied for a possible replacement for liquid electrolytes. However, it results in degradation of mechanical properties and short circuit during cycling at the high temperature (60~80°C). Therefore, the thickness of electrolytes is required to be 150㎛ or more. However, to improve the energy density of all-solid state battery, it is required to reduce the thickness of the solid electrolyte layer to as low as 50㎛ and less. As a method for reducing the thickness, we suggested that the thin solid composite electrolyte film was composed of PEO/PVDF blending polymer as ionic conductor and binder including lithium salts and garnet LLZO powders. In addition, the composite cathode slurry was composed of NCM active material, Super P, Garnet-type LLZO powder and PEO/PVDF blending polymer. The electrochemical properties were measured by the AC impedance method, Linear Sweep Voltammetry, Symmetrical cell test and charge/discharge cell test. As a result, we will introduce the properties of CE with garnet LLZO powder, PEO and PVDF polymers in cathode and solid electrolyte layer. Finally, a pouch-type ASSBs having a bipolar structure in which energy density is improved by applying such a thin SE is described in more detail.